/*
 * Copyright (c) 2010, 2020 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.glassfish.grizzly.http.util;

import java.io.ByteArrayOutputStream;

/**
 * Library of utility methods useful in dealing with converting byte arrays to and from strings of hexadecimal digits.
 * Code from Ajp11, from Apache's JServ.
 *
 * @author Craig R. McClanahan
 */

public final class HexUtils {

    // -------------------------------------------------------------- Constants

    /**
     * Table "isHexDigit".
     */
    static final boolean[] IS_HEX_DIGIT = { false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, true, true, true, true, true, true, true, true, true, true, false,
            false, false, false, false, false, false, true, true, true, true, true, true, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, true, true, true, true, true,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false,
            false, false, false, false, false, false, };

    /**
     * Table for HEX to DEC byte translation.
     */
    static final int[] DEC = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 00, 01, 02, 03, 04, 05, 06, 07, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13,
            14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, };

    /**
     * Table for DEC to HEX byte translation.
     */
    static final byte[] HEX = { (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
            (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f' };

    // --------------------------------------------------------- Static Methods

    /**
     * Convert a String of hexadecimal digits into the corresponding byte array by encoding each two hexadecimal digits as a
     * byte.
     *
     * @param digits Hexadecimal digits representation
     *
     * @exception IllegalArgumentException if an invalid hexadecimal digit is found, or the input string contains an odd
     * number of hexadecimal digits
     */
    public static byte[] convert(String digits) {

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        for (int i = 0; i < digits.length(); i += 2) {
            char c1 = digits.charAt(i);
            if (i + 1 >= digits.length()) {
                throw new IllegalArgumentException("hexUtil.odd");
            }
            char c2 = digits.charAt(i + 1);
            byte b = 0;
            if (c1 >= '0' && c1 <= '9') {
                b += (c1 - '0') * 16;
            } else if (c1 >= 'a' && c1 <= 'f') {
                b += (c1 - 'a' + 10) * 16;
            } else if (c1 >= 'A' && c1 <= 'F') {
                b += (c1 - 'A' + 10) * 16;
            } else {
                throw new IllegalArgumentException("hexUtil.bad");
            }
            if (c2 >= '0' && c2 <= '9') {
                b += c2 - '0';
            } else if (c2 >= 'a' && c2 <= 'f') {
                b += c2 - 'a' + 10;
            } else if (c2 >= 'A' && c2 <= 'F') {
                b += c2 - 'A' + 10;
            } else {
                throw new IllegalArgumentException("hexUtil.bad");
            }
            baos.write(b);
        }
        return baos.toByteArray();

    }

    /**
     * Convert a byte array into a printable format containing a String of hexadecimal digit characters (two per byte).
     *
     * @param bytes Byte array representation
     */
    public static String convert(byte bytes[]) {

        StringBuilder sb = new StringBuilder(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++) {
            sb.append(convertDigit(bytes[i] >> 4));
            sb.append(convertDigit(bytes[i] & 0x0f));
        }
        return sb.toString();

    }

    /**
     * Convert 4 hex digits to an int, and return the number of converted bytes.
     *
     * @param hex Byte array containing exactly four hexadecimal digits
     *
     * @exception IllegalArgumentException if an invalid hexadecimal digit is included
     */
    public static int convert2Int(byte[] hex) {
        // Code from Ajp11, from Apache's JServ

        // assert b.length==4
        // assert valid data
        int len;
        if (hex.length < 4) {
            return 0;
        }
        if (DEC[hex[0]] < 0) {
            throw new IllegalArgumentException("hexUtil.bad");
        }
        len = DEC[hex[0]];
        len = len << 4;
        if (DEC[hex[1]] < 0) {
            throw new IllegalArgumentException("hexUtil.bad");
        }
        len += DEC[hex[1]];
        len = len << 4;
        if (DEC[hex[2]] < 0) {
            throw new IllegalArgumentException("hexUtil.bad");
        }
        len += DEC[hex[2]];
        len = len << 4;
        if (DEC[hex[3]] < 0) {
            throw new IllegalArgumentException("hexUtil.bad");
        }
        len += DEC[hex[3]];
        return len;
    }

    public static int[] getDecBytes() {
        return DEC.clone();
    }

    /**
     * [Private] Convert the specified value (0 .. 15) to the corresponding hexadecimal digit.
     *
     * @param value Value to be converted
     */
    private static char convertDigit(int value) {

        value &= 0x0f;
        if (value >= 10) {
            return (char) (value - 10 + 'a');
        } else {
            return (char) (value + '0');
        }

    }

    public static boolean isHexDigit(byte c) {
        return IS_HEX_DIGIT[c];
    }

    public static boolean isHexDigit(int c) {
        return IS_HEX_DIGIT[c];
    }

    public static int hexDigit2Dec(byte hexDigit) {
        return DEC[hexDigit];
    }

    public static int hexDigit2Dec(int hexDigit) {
        return DEC[hexDigit];
    }
}
